Receptor-binding domain of SARS-CoV-2 spike protein efficiently inhibits SARS-CoV-2 infection and attachment to mouse lung

Abstract

COVID-19, caused by a novel coronavirus, SARS-CoV-2, poses a serious global threat. It was first reported in 2019 in China and has now dramatically spread across the world. It is crucial to develop therapeutics to mitigate severe disease and viral spread. The receptor-binding domains (RBDs) in the spike protein of SARS-CoV and MERS-CoV have shown anti-viral activity in previous reports suggesting that this domain has high potential for development as therapeutics. To evaluate the potential antiviral activity of recombinant SARS-CoV-2 RBD proteins, we determined the RBD residues of SARS-CoV-2 using a homology search with RBD of SARS-CoV. For efficient expression and purification, the signal peptide of spike protein was identified and used to generate constructs expressing recombinant RBD proteins. Highly purified RBD protein fused with the Fc domain of human IgG showed potent anti-viral efficacy, which was better than that of a protein fused with a histidine tag. Intranasally pre-administrated RBD protein also inhibited the attachment of SARS-COV-2 to mouse lungs. These findings indicate that RBD protein could be used for the prevention and treatment of SARS-CoV-2 infection.

SARS‐CoV‐2 spike spurs intestinal inflammation via VEGF production in enterocytes

“…In order to validate whether SARS‐CoV‐2 was responsible for the VEGF production in intestinal tissue, we generated an animal model to specifically mimic the intestinal inflammation by intraperitoneally injecting the recombinant spike‐Fc containing the receptor binding domain (RBD) to C57BL/6J mice (Fig EV2A). Co‐localization of murine ACE2 with spike was confirmed by immunofluorescence staining (Fig EV2B–D), which was consistent with previous results (Kuba et al , 2005; Raghavan et al , 2021; Shin et al , 2021). Since intestinal mucosal barrier renders strong protection from the infectious agents (Sharma & Riva, 2020), treating mice with spike RBD alone for a short time only gave rise to mild inflammation (Fig EV2E).…”

“…Here, we provide an alternative route by showing that the ERK/VEGF axis in enterocytes plays a pivotal role in SARS‐CoV‐2‐induced intestinal inflammation. However, we have no adequate evidence to support the mediating role of ACE2 in the SARS‐CoV‐2 spike‐induced effects since the affinity of murine ACE2 and SARS‐CoV‐2 spike is still debatable (Li et al , 2004; Kuba et al , 2005; Zhao et al , 2020; Gu et al , 2021; Nuovo et al , 2021; Raghavan et al , 2021; Shin et al , 2021; Wang et al , 2021). We consider that whether the effect of spike RBD is through or fully through ACE2 is beyond the scope of this work.…”

Feline Coronavirus Infection of Domestic Cats Causes Development of Cross-Reactive Antibodies to SARS-CoV-2 Receptor Binding Domain

“…This is slightly more than twice the dose used by Shin et al . to block SCoV2 infection of Vero cells with SCoV2 RBD-His [57]. The ability for SCoV2 RBD to cross-protect against in vitro FCoV2 infection, although weaker than that of FCoV2 RBD, further supports our finding that SCoV2 RBD and FCoV2 RBD may be structurally and antigenically similar.…”

“…The novelty of our study is that SCoV2 UF-RBD at a high concentration was able to cross-block or cross-protect against FCoV2 infection of feline cell line at a RBD dose of 48-68 μg/mL without any cellular toxicity (Fig 4A). This is slightly more than twice the dose used by Shin et al to block SCoV2 infection of Vero cells with SCoV2 RBD-His [57]. The ability for SCoV2 RBD to cross-protect against in vitro FCoV2 infection, although weaker than that of FCoV2 RBD, further supports our finding that SCoV2 RBD and FCoV2 RBD may be structurally and antigenically similar.…”

“…Shin et al . determined that RBD-Fc tag was better at in vitro inhibition of SCoV2 infection than RBD-His [57]. Since FCoV2 RBD had extended amino-end and blocked infection more efficiently, we reasoned that a slightly larger SCoV2 RBD may block the in vitro infection against SCoV2 and FCoV2 better than a CoV-nonspecific tag as long as it retains the native conformation.…”